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Waste not, want not

This cellulose aerogel, made of recycled paper, can soak up to 90 times its dry weight

NUS Engineering scientists have achieved a world’s first in converting paper waste into cellulose aerogels at an extremely low price point and in half the time of the existing method. The light, porous and low-density material has a plethora of applications including oil spill clean-up, heat insulation and packaging.

Assistant Professor Duong Hai Minh from NUS Mechanical Engineering, who led the team, said, “Traditional aerogels are mainly made of silica, which is not environmentally friendly. In contrast, cellulose is low cost and makes up 75 to 85 per cent of recycled paper.”

Existing cellulose aerogels are made from virgin pulp, but the NUS breakthrough — using recycled paper — consumes 70 per cent less energy. It also releases fewer polluting emissions and requires less dioxins, which are toxic, in the chlorine bleaching process.

The hydrophilic cellulose aerogels can soak up oil because they have been coated with Trimethoxy-methylsilane (MTMS), which cause them to repel water. The present method of cleaning oil spills uses Polypropylene (PP)-based absorbents that cost $6-11 (US$4-8) per piece, whereas the NUS invention costs a fraction of that amount for an equivalent-sized piece. Another cost-saver is the fact that cellulose fibre from paper waste is priced at $1.40 per ton.

Among the advantages of using these aerogels to clean up oil spills are: an absorption capacity of up to 90 times its dry weight at a rate four times faster than current commercial sorbents; 99 per cent recovery of absorbed crude oil from the aerogels; biodegradability, unlike PP-based absorbents; and ease-of-use, as the oil spill does not need to be primed first to separate oil and water. Asst Prof Duong estimates the potential market size for this application to be over $200 billion.

The team that developed these affordable and efficient aerogels include (from left) Year 4 NUS Mechanical Engineering students Siah Jie Yang and Bowen Gu, and Asst Prof Duong

Building insulation is also another viable application for the aerogels, because of their low thermal conductivity, with a potential market of $4.6 billion globally. Their water-repellant property suits both dry and wet climes, and their structure remains stable for years in tropical climates, explained Asst Prof Duong.

Other possible applications for the novel product include: packing materials, replacing less-environmentally friendly plastic-based materials such as bubble wrap; personal hygiene products such as diapers and sanitary napkins; and an affordable alternative to the XStat syringe — which costs $280-420 — that plugs up life-threatening wounds in seconds.

NUS Industry Liaison Office has licensed the technology to Bronxculture Pte Ltd in November 2015 for commercialisation. The company intends to manufacture the paper-waste aerogels and expand its application in the areas of insulation, packaging and winter wear; and as an oil-absorption material. The product will be commercially available worldwide in a year’s time. The team has filed a patent for their invention in the US, China, India and several Southeast-Asian countries including Thailand and Vietnam.